1. Field of the Invention
The present invention relates to a vehicle electronic control method and system for controlling a vehicle by using A/D-converted values of detection signals from various sensors for controlling the vehicle.
2. Related Art
Among systems in which electronic fuel injection (EFI), electronic ignition spark advance (ESA) and the like are processed in one electronic control unit (ECU), there has been known one in which a sub-microcomputer for discriminating whether or not there occurs a knock is separately constructed from a main microcomputer for performing the other vehicular controls because signal processing for the knock control is complicated.
There has been also known in which an A/D converter for A/D-converting (analog to digital converting) sensor signals from various sensors is built in the sub-microcomputer and an A/D conversion request is output from the main microcomputer to the sub-microcomputer.
In order to simplify the process for outputting the A/D conversion request in the microcomputer, it is proposed to cause the A/D converter to output the A/D conversion request to a plurality of channels in batch (continuously) by a hardware circuit different from a CPU within the microcomputer just by instructing the A/D conversion request time-synchronously by the CPU, i.e., at every constant time interval.
However, when this is adopted to the system having the knock control, A/D conversion of a knock signal for controlling the knock may be activated in the sub-microcomputer during when the A/D converter in the sub-microcomputer side executes the A/D conversion requested by the main microcomputer. It is because the A/D conversion process of the knock signal has to be executed time-asynchronously, more specifically, at every angular rotation of a crankshaft of an internal combustion engine.
Here, if the A/D conversion process in the A/D converter of the sub-microcomputer requested by the main microcomputer overlaps with the A/D conversion process for the knock control via the A/D converter of the sub-microcomputer itself, either one of the A/D-converted values will be necessarily broken. As the A/D-conversion for the knock control is preceded in the sub-microcomputer due to its importance in the vehicular control and the time synchronous A/D-converted value will be sent to the main microcomputer in the state where it is broken.
The A/D-converted values produced by the time-synchronous A/D conversion process also corresponds to important parameters, e.g., a parameter for finding a variation per constant time. Data of such parameters must be taken in corresponding to the output timing of the A/D conversion request. Thus, there will occur a problem that the vehicular control is troubled when the A/D-converted value is broken.